客户说我的***系统登录时密码是明文传输，不高兴，我对HTTPS不太了解，那我用MD5加密下，虽然不能保证万无一失，但也好过明文传输嘛。
说下大概的过程：打开登录的JSP页面时，生成一个随机字符串，放在session里面，以便后台也可以拿到。客户输入用户名和密码点击"登录"时，拿到密码和随机字符串，拼接在一起后利用js生成MD5字符串。然后用js把那个password的value改成MD5字符串，再提交表单。
后台拿到随机字符串和用户名和MD5字符串，通过用户名到数据库查询密码，用密码和随机字符串拼接在一起生成MD5字符串，用生成的MD5字符串和前台传过来的MD5字符串进行匹配，如果一致就通过验证。
------------------------------前台-------------------------------------
jsp页面生成随机数：
<%
String pageName = pageContext.getRequest().getParameter("pageName");
pageName = StringUtils.filterUnsafeChars(pageName); //业务系统内部的一个过滤操作，可以跳过这一步
//产生随机数，和密码一起生成MD5
request.getSession().setAttribute("md5RandomKey", StringUtils.getRandomNum(10));
%>
表单submit时调用下面的函数：
function encryptionPassword(){
var hash = MD5($("user_password").value+"${md5RandomKey}");
$("user_password").value = hash;
}
md5.js如下：
/*
* A JavaScript implementation of the RSA Data Security, Inc. MD5 Message
* Digest Algorithm, as defined in RFC 1321.
* Copyright (C) Paul Johnston 1999 - 2000.
* Updated by Greg Holt 2000 - 2001.
* See http://pajhome.org.uk/site/legal.html for details.
*/
var hex_chr = "0123456789abcdef";
function rhex(num) {
str = "";
for (j = 0; j <= 3; j++) {
str += hex_chr.charAt((num >> (j * 8 + 4)) & 15) + hex_chr.charAt((num >> (j * 8)) & 15);
}
return str;
}
function str2blks_MD5(str) {
nblk = ((str.length + 8) >> 6) + 1;
blks = new Array(nblk * 16);
for (i = 0; i < nblk * 16; i++) {
blks[i] = 0;
}
for (i = 0; i < str.length; i++) {
blks[i >> 2] |= str.charCodeAt(i) << ((i % 4) * 8);
}
blks[i >> 2] |= 128 << ((i % 4) * 8);
blks[nblk * 16 - 2] = str.length * 8;
return blks;
}
function add(x, y) {
var lsw = (x & 65535) + (y & 65535);
var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
return (msw << 16) | (lsw & 65535);
}
function rol(num, cnt) {
return (num << cnt) | (num >>> (32 - cnt));
}
function cmn(q, a, b, x, s, t) {
return add(rol(add(add(a, q), add(x, t)), s), b);
}
function ff(a, b, c, d, x, s, t) {
return cmn((b & c) | ((~b) & d), a, b, x, s, t);
}
function gg(a, b, c, d, x, s, t) {
return cmn((b & d) | (c & (~d)), a, b, x, s, t);
}
function hh(a, b, c, d, x, s, t) {
return cmn(b ^ c ^ d, a, b, x, s, t);
}
function ii(a, b, c, d, x, s, t) {
return cmn(c ^ (b | (~d)), a, b, x, s, t);
}
function MD5(str) {
x = str2blks_MD5(str);
var a = 1732584193;
var b = -271733879;
var c = -1732584194;
var d = 271733878;
for (i = 0; i < x.length; i += 16) {
var olda = a;
var oldb = b;
var oldc = c;
var oldd = d;
a = ff(a, b, c, d, x[i + 0], 7, -680876936);
d = ff(d, a, b, c, x[i + 1], 12, -389564586);
c = ff(c, d, a, b, x[i + 2], 17, 606105819);
b = ff(b, c, d, a, x[i + 3], 22, -1044525330);
a = ff(a, b, c, d, x[i + 4], 7, -176418897);
d = ff(d, a, b, c, x[i + 5], 12, 1200080426);
c = ff(c, d, a, b, x[i + 6], 17, -1473231341);
b = ff(b, c, d, a, x[i + 7], 22, -45705983);
a = ff(a, b, c, d, x[i + 8], 7, 1770035416);
d = ff(d, a, b, c, x[i + 9], 12, -1958414417);
c = ff(c, d, a, b, x[i + 10], 17, -42063);
b = ff(b, c, d, a, x[i + 11], 22, -1990404162);
a = ff(a, b, c, d, x[i + 12], 7, 1804603682);
d = ff(d, a, b, c, x[i + 13], 12, -40341101);
c = ff(c, d, a, b, x[i + 14], 17, -1502002290);
b = ff(b, c, d, a, x[i + 15], 22, 1236535329);
a = gg(a, b, c, d, x[i + 1], 5, -165796510);
d = gg(d, a, b, c, x[i + 6], 9, -1069501632);
c = gg(c, d, a, b, x[i + 11], 14, 643717713);
b = gg(b, c, d, a, x[i + 0], 20, -373897302);
a = gg(a, b, c, d, x[i + 5], 5, -701558691);
d = gg(d, a, b, c, x[i + 10], 9, 38016083);
c = gg(c, d, a, b, x[i + 15], 14, -660478335);
b = gg(b, c, d, a, x[i + 4], 20, -405537848);
a = gg(a, b, c, d, x[i + 9], 5, 568446438);
d = gg(d, a, b, c, x[i + 14], 9, -1019803690);
c = gg(c, d, a, b, x[i + 3], 14, -187363961);
b = gg(b, c, d, a, x[i + 8], 20, 1163531501);
a = gg(a, b, c, d, x[i + 13], 5, -1444681467);
d = gg(d, a, b, c, x[i + 2], 9, -51403784);
c = gg(c, d, a, b, x[i + 7], 14, 1735328473);
b = gg(b, c, d, a, x[i + 12], 20, -1926607734);
a = hh(a, b, c, d, x[i + 5], 4, -378558);
d = hh(d, a, b, c, x[i + 8], 11, -2022574463);
c = hh(c, d, a, b, x[i + 11], 16, 1839030562);
b = hh(b, c, d, a, x[i + 14], 23, -35309556);
a = hh(a, b, c, d, x[i + 1], 4, -1530992060);
d = hh(d, a, b, c, x[i + 4], 11, 1272893353);
c = hh(c, d, a, b, x[i + 7], 16, -155497632);
b = hh(b, c, d, a, x[i + 10], 23, -1094730640);
a = hh(a, b, c, d, x[i + 13], 4, 681279174);
d = hh(d, a, b, c, x[i + 0], 11, -358537222);
c = hh(c, d, a, b, x[i + 3], 16, -722521979);
b = hh(b, c, d, a, x[i + 6], 23, 76029189);
a = hh(a, b, c, d, x[i + 9], 4, -640364487);
d = hh(d, a, b, c, x[i + 12], 11, -421815835);
c = hh(c, d, a, b, x[i + 15], 16, 530742520);
b = hh(b, c, d, a, x[i + 2], 23, -995338651);
a = ii(a, b, c, d, x[i + 0], 6, -198630844);
d = ii(d, a, b, c, x[i + 7], 10, 1126891415);
c = ii(c, d, a, b, x[i + 14], 15, -1416354905);
b = ii(b, c, d, a, x[i + 5], 21, -57434055);
a = ii(a, b, c, d, x[i + 12], 6, 1700485571);
d = ii(d, a, b, c, x[i + 3], 10, -1894986606);
c = ii(c, d, a, b, x[i + 10], 15, -1051523);
b = ii(b, c, d, a, x[i + 1], 21, -2054922799);
a = ii(a, b, c, d, x[i + 8], 6, 1873313359);
d = ii(d, a, b, c, x[i + 15], 10, -30611744);
c = ii(c, d, a, b, x[i + 6], 15, -1560198380);
b = ii(b, c, d, a, x[i + 13], 21, 1309151649);
a = ii(a, b, c, d, x[i + 4], 6, -145523070);
d = ii(d, a, b, c, x[i + 11], 10, -1120210379);
c = ii(c, d, a, b, x[i + 2], 15, 718787259);
b = ii(b, c, d, a, x[i + 9], 21, -343485551);
a = add(a, olda);
b = add(b, oldb);
c = add(c, oldc);
d = add(d, oldd);
}
return rhex(a) + rhex(b) + rhex(c) + rhex(d);
}
-------------------------后台----------------------------------
拿到随机字符串：
String md5RandomKey = (String)request.getSession().getAttribute("md5RandomKey");
拿到密码（MD5字符串）：
String md5Password = request.getParameter("user_password");
然后通过用户名到数据库查询该用户的密码，如果用户不存在则提前提示错误。
拿到数据库的密码后和上面的随机字符串（md5RandomKey）一起生成MD5字符串:
String md5Password_real = StringUtils.getMD5Str(attendant.getPassword()+md5RandomKey,null);
最后拿 md5Password_real和md5Password 进行比较，一致则通过验证。
下面是上面代码用到的在StringUtils下的两个函数：
1：获取随机字符串：
private static final String ALLCHAR = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
/**
* 获取任意位的随机字符串(0-9 a-z A-Z)
* @param size 位数
* @return
*/
public static final String getRandomNum(int size){
StringBuffer sb = new StringBuffer();
Random random = new Random();
for (int i = 0; i < size; i++) {
sb.append(ALLCHAR.charAt(random.nextInt(ALLCHAR.length())));
}
return sb.toString();
}
2：生成MD5字符串：
/**
* md5加密(ITS)
* @param str
* @param charSet
* @return
*/
public synchronized static final String getMD5Str(String str,String charSet) { //md5加密
MessageDigest messageDigest = null;
try {
messageDigest = MessageDigest.getInstance("MD5");
messageDigest.reset();
if(charSet==null){
messageDigest.update(str.getBytes());
}else{
messageDigest.update(str.getBytes(charSet));
}
} catch (NoSuchAlgorithmException e) {
log.error("md5 error:"+e.getMessage(),e);
} catch (UnsupportedEncodingException e) {
log.error("md5 error:"+e.getMessage(),e);
}
byte[] byteArray = messageDigest.digest();
StringBuffer md5StrBuff = new StringBuffer();
for (int i = 0; i < byteArray.length; i++) {
if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)
md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));
else
md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));
}
return md5StrBuff.toString();
}
上面的MessageDigest所在的包是： java.security.MessageDigest